Pipe protectors are tubular rubber members that surround pipe used in downhole drilling operations. The rubber pipe protector serves as a bumper for the pipe which is generally introduced into metal casing in the well hole. The pipe protector should fit snugly around the outside diameter of the pipe. During the drilling operation the pipe is rotated rapidly. If the pipe protector is not secure, slippage can occur and the pipe protector will slide off of the desired location on the pipe.
Reliable pipe protectors are necessary during directional drilling operations during which process the well is drilled at an angle in a non-vertical direction. The pipe will contact the casing wall with metal to metal contact that causes wear on the pipe. By spacing pipe protectors along the pipe string, the rubber pipe protectors rather than the pipe contact the well casing.
A typical pipe protector well known to those in the art is a split type pipe protector. The tubular rubber member is typically about 4 to 12 inches in length and has an opening the length of the member that can be further opened to facilitate installation onto the pipe. After the pipe is enclosed and encircled by the pipe protector, the rubber tubular member is secured or fastened. Many split type pipe protectors have interlocking metal teeth covered by rubber and close with a key fastener inserted lengthwise through the teeth. The metal teeth are connected to a cylindrical metal insert inside the tubular rubber member. The metal insert may be smooth or corrugated metal.
The inner diameter of the pipe protector is sized to match the outer diameter of the drill pipe. The conventional pipe protectors are sensitive to the outer diameter dimension of the pipe on which they are installed. Changes in the outer diameter of the pipe of about (-)0.010 inch reduce the gripping forces of the pipe protector and allow the protector to slip or rotate on the pipe at relatively low side forces. Drill pipe commonly can vary in outer diameter by -0.05% depending on pipe size. Conventional pipe protectors slip on the undersized pipe and fail to provide the desired bumper effect and can be detrimental to the drilling operation. It is possible to lose the pipe protector downhole. The drilling operation must then be shut down to fish out the pipe protector. Slipping of undersized pipe protectors on drill pipe is a serious problem. Attempts to alleviate this problem have included wrapping strips of rubber around the pipe circumference before placing the pipe protector onto the pipe. Although this method was moderately successful in reducing slippage, it is tedious and impractical in field applications.
The present invention provides a variable diameter pipe protector that prevents slipping on undersized pipe, but can also be used on full sized pipe. A pipe protector capable of surrounding a full size outer diameter pipe is provided with at least one rubber flap attached to the inside surface. In one embodiment the rubber flap attached to the inside surface can be cut. The severed portion is removed leaving the remaining portion of the flap attached. The flap provides sufficient inner diameter thickness to compensate for the undersized pipe. The smaller the diameter of the pipe the more of the flap is left inside the pipe protector to serve as additional volume of rubber needed to give a tight grip on the pipe. In a preferred embodiment the flap extends substantially the length of the rubber tubular member. If the pipe is sized to the full diameter, the flap is completely detachable and can be removed. The pipe protector can be a split type design with an opening the length of the rubber tubular member. The opening the length of the tubular rubber member is capable of separation to facilitate the introduction of the pipe. A closing means is used to secure the pipe protector for installation after the flap material has been cut and detached. The cylindrical metal insert with interlocking metal teeth is typically included in this design.
In an alternative embodiment, multiple detachable rubber flaps are attached to the inside surface of the pipe protector. During installation of the pipe protector on the pipe, as many flaps as needed to provide a tight grip are left attached to the inside the pipe protector. The flap or flaps are preferably attached with an adhesive for relatively easy removal. The flaps are placed on the inside surface of the rubber tubular member so as not to overlap each other.
Conventional split type pipe protectors can be adapted with a detachable flap or flaps to accompany undersized pipe of various diameters.